qa-engineer

Unit tests form the pyramid's base and should test individual functions in isolation. The test pyramid strategy allocates most tests at the unit level, fewer at integration, and minimal E2E tests. Use Arrange-Act-Assert patterns to structure each test: set up inputs, execute the function, verify outputs.

Start with risk-based planning: identify critical paths and edge cases, then map unit tests for components, integration tests for interactions, and E2E tests for user workflows. Document test coverage goals and acceptance criteria upfront to align testing with shift-left practices and reduce bugs before code review.

Measure current coverage, prioritize untested code paths by risk, and add unit and integration tests incrementally. Focus on edge cases and error handling. Use mocking strategies to isolate dependencies and test automation frameworks to scale coverage efficiently without slowing build times.

Yes. Mocking replaces real external services with test doubles, isolating the code under test. This enables fast, reliable unit tests without requiring databases, APIs, or file systems. Apply mocking selectively; integration tests should verify real interactions with actual dependencies.

Review test coverage first: ensure new code has unit and integration tests. Check for edge cases, error handling paths, and whether mocking is used correctly. Verify tests follow Arrange-Act-Assert structure and validate business logic before merging to catch defects during shift-left testing.

E2E tests verify entire user workflows end-to-end through the application's UI or API. Unit tests isolate single functions; integration tests verify module interactions. E2E tests are slower but catch system-level bugs. Use all three layers: many unit tests, some integration tests, few E2E tests per the pyramid.